Understanding the carrier (IMEI) unlock process

Hi Folks,

I'm in a bit of trouble with a carrier unlock process that's driving me nuts! I'm completely new to this and I'm learning on my feet, but any help would be fab.

The story goes that I bought an iPhone 7 of ebay (UK). I was sold as locked to Verizon which didn't really bother me, until now!

I used a third party unlock service and waited 7 days for the unlock to come through. Once given the go ahead I tried, as instructed, to process the unlock. I tried to put the new sim card that I wanted to use in and unlock through iTunes, No joy. I've tried to back up and restore. I've tried to wipe the phone then restore from backup. I have tried everything that any forums have suggested and watched lots of youtube vids to gain a better knowledge but nothing.

I have then contact Verizon who looked into an IMEI unlock for me but they say they aren't the carrier of the phone. Long story short they say they further investigated the phone and that it was already unlocked. The GSX report I have however tells me it's locked to "US GSM & Verizon"

I then contacted Apple who couldn't do a great deal for me really except prompt me to ask the other big two companies in the US if they recognised the IMEI number.

I contacted AT&T and connected to a lovely lady who couldn't help enough. In a nuts shell she told me that on her screen it definitely was Verizon as the carrier and that indeed the phone was unlocked, so there was an element of truth to what I was told by Verizon.

No matter what I do I can't get this pain in the backside to update the carrier setting from iTunes.

My questions are :-

1). Can anyone unlock from any iTunes account unlock an iPhone device if it released from the carrier, or is it only the original registered owner/iCloud account that can unlock the device?

2). Does the carrier have the ability to recall the IMEI unlock if the original owner didnt complete the process?

3). Can I purchase a Verizon sim card, use it for 1 week/month, then claim the unlock for myself?

Thank In Advance

Danny,